The first thing to know about the green crab is that it isn’t necessarily green. Fresh out of the ocean in southwestern Nova Scotia, it can appear brown, or red, or yellow. What is distinctive is its spiked shell that tapers at the top into 13 spines, like a crown worn by the leader of an invading army—which is appropriate enough, since the second thing you need to know about the green crab is that it’s one of the planet’s most aggressive invasive species. In its path toward world domination, the European green crab—which, as the name suggests, originally hails from Europe, as well as North Africa—has acquired a lot of titles: “cockroach of the sea” and “one of the 10 most unwanted species in the world.” In Nova Scotia, fisherman Jeff Roy has come up with his own moniker.